Microphone goes dead after 15.7.5, comes back after reset for a bit

Thanks, I suspected. These are signs of an  AudioIC hardware issue for iPhone 7 models. It may eventually become a consistent issue. You can:

1. Do an out-of-warranty replacement of your iPhone.
2. Trade in your iPhone towards a new one.
3. Find a competent 3rd party repair site that can do the soldering repairs need, but no guarantees. Also, if you go this route Apple may refuse service on your iPhone in the future.

Hello Jeffooo,

Thank you for using Apple Support Communities. We’d like to help out with your microphone issue. If you noticed that your microphone isn’t properly working on your iPhone, then we recommend that you review the following resource. You’ll find steps that you can try that could help: If the microphones on your iPhone aren't working - Apple Support

Also, if your iPhone is compatible, it would be a good idea to update to iOS 16. This can usually help with unique issues, since updates include fixes. Just in case, this link can guide you through the update process: Update your iPhone or iPad - Apple Support

1.)Back up your device using iCloud or your computer.

2.)Plug your device into power and connect to the internet with Wi-Fi.

3.)Go to Settings > General, then tap Software Update.

4.) If you see more than one software update option available, choose the one that you want to install.

5.) Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now. If you don't know your passcode, learn what to do.

If these steps don't help out, please reach out to Apple Support. They might have to get your iPhone evaluated. Just in case, you can use this link to reach them: Get Support

Thank you for using Apple Support Communities. Take care.

What model iPhone?

Hello Jeffooo,

Since your issue persists, we recommend you reach out to Apple Support for additional assistance. You can reach them: Get Support

Best Regards.